100-Amp vs. 200-Amp vs. 400-Amp Service: Which Does Your Home Need?
You want to add an EV charger, but your breakers already trip. Now you wonder if your home has enough power. Adding more without enough service can be risky. The answer starts with your amp service size.
Most homes today run on either 100 or 200 amps. But which one is right for yours? The size you choose shapes every upgrade you make. It also affects your safety and comfort.
Below, we compare 100-amp, 200-amp, and 400-amp service so you know which your home needs. You will learn what each size can power and how to check what you have now. We also help you size for future plans, like an EV charger or heat pump.
100-Amp vs. 200-Amp vs. 400-Amp: The Quick Answer
Most homes need one of three service sizes. Each one offers a different amount of power. Here is how they compare at a glance.
| Service size | Power capacity | Best for |
|---|---|---|
| 100-amp | About 24,000 watts | Older or smaller homes with gas heat |
| 200-amp | About 48,000 watts | Most modern homes today |
| 400-amp | About 96,000 watts | Large or all-electric homes |
A 100-amp service was standard in many older homes. It works for smaller homes with gas appliances. A 200-amp service is now the modern standard for most homes.
A 400-amp service is built for heavy demand. It usually comes as two linked 200-amp panels. Most homes today land on 200-amp service.
What Each Service Size Can Power
The right size depends on what you plug in. Each level handles a different load. Here is what each one can run.
- 100-amp. Powers lights, outlets, and gas appliances. It gets tight with central AC.
- 200-amp. Runs AC, an electric range, a dryer, and an EV charger. It also supports home additions.
- 400-amp. Handles multiple HVAC zones, dual EV chargers, a hot tub, or a workshop.
One detail surprises many homeowners. A 100-amp panel only safely supplies about 80 amps. That leaves little room for big modern appliances.
Most North Austin homes we see do well on 200-amp service. It covers daily needs with room to grow. We help you match the size to your real load.
How to Tell What Service You Have Now
You can check your service size in seconds. The answer sits right on your main breaker. Here is how to find it safely.
- Open the panel door. Find the large main breaker at the top or bottom.
- Read the handle. Look for a number stamped on it, like 100, 200, or 400.
That number is your answer. It shows your home's total service size.
This method works about 95% of the time. Never remove the panel cover to look deeper. The space behind it carries live, dangerous power.
One more note on subpanels. A subpanel adds more circuit slots, not more total power. Your main breaker still sets your home's true capacity.
Sizing for the Future: EVs, Heat Pumps, and More
The right size today should fit tomorrow too. Modern homes keep adding power-hungry features. Plan ahead so you do not upgrade twice.
- EV chargers. These draw heavy power for hours at a time.
- Heat pumps. All-electric heating and cooling raises your total demand.
- Plan for 5 to 10 years. Think about additions, a hot tub, or a workshop.
- Choose extra slots. A panel with more circuit spaces gives you room to grow.
There is good news for many homes. A 200-amp service plus smart load management can often avoid a 400-amp jump. That keeps your upgrade simpler and your home ready.
We recently sized a panel for a North Austin family adding an EV charger. Planning for your next upgrade? Explore our North Austin electrical services and we will help you size it right.
Which Size Should You Choose?
The right size comes down to your home and your plans. Use these simple guidelines to point you the right way.
- Small, older, gas-heat home with no big plans? 100-amp may hold, but 200-amp is safer.
- A typical home with AC and an EV charger? 200-amp service is the right fit.
- A large or all-electric home with multiple EVs or a workshop? 400-amp service fits best.
Remember that these are starting points, not a final answer. The only sure way to size your service is a load calculation. We measure your real demand, not a rough guess.
One rule matters above all. Never try a panel upgrade yourself. The Electrical Safety Foundation International warns that faulty wiring and panels are a leading cause of home fires.
Get a Free Load Calculation in North Austin
The best way to size your service is with real numbers. For most homes, 200-amp service is the right fit. We confirm your exact need with a load calculation.
Our process is clear from start to finish. We run the calculation, check your panel, and recommend the right size. We also pull permits and back our work with an electrical panel lifetime warranty.
We serve North Austin and nearby areas, including Round Rock, Cedar Park, Pflugerville, and Georgetown. As Abacus Plumbing, Air Conditioning, & Electrical, we have powered local homes since 2003.
Ready to size your service? Call (512) 943-7070 today to schedule your electrical panel upgrade.
Frequently Asked Questions
Most modern homes need 200-amp service, which is the current standard. Smaller older homes with gas heat may run on 100-amp. Large or all-electric homes often need 400-amp service.
Open your panel door and read the number on the main breaker handle. It will show 100, 200, or 400, which is your service size. Never remove the panel cover to look deeper.
For most modern homes, 100-amp service is no longer enough. A 100-amp panel only safely supplies about 80 amps. That leaves little room for central AC, an EV charger, or electric appliances.
No, most homes can add an EV charger on 200-amp service. A 400-amp service is for large homes with multiple EVs, heat pumps, or a workshop. We run a load calculation to confirm your exact need.
No, a panel upgrade should always be done by a licensed electrician. The main breaker connects to live service wires that carry deadly power. Doing it yourself risks shock, fire, and code violations.